Intermediates of myocardial mitochondrial beta-oxidation: possible channelling of NADH and of CoA esters

Adult rat heart mitochondria were isolated and incubated with [U-C-14]hexad ecanoyl-CoA or unlabelled hexadecanoyl-CoA. The accumulating CoA and carnit ine esters and [NAD(+]/)[NADH] ratio were measured by HPLC or tandem mass s pectrometry. Despite minimal changes in the intramitochondrial [NAD(+)]/[NA DH] ratio, 2,3-unsaturated and 3-hydroxyacyl esters were observed as well a s saturated acyl-CoA and acylcarnitine eaters. In addition to acetylcarniti ne, significant amounts of butyryl-, hexanoyl-, octanoyl- and decanoylcarni tines were detected and measured. Rat myocardial beta-oxidation is subject to control at the level of 3-hydroxyacyl-CoA dehydrogenase but this control is not due to a simple lack of oxidised NAD. We hypothesise a pool of NAD in contact between the trifunctional protein of beta-oxidation and complex I of the respiratory chain, the turnover of which is responsible for some o f the control of beta-oxidation flux. In addition, short- and medium-chain acylcarnitine eaters were detected whereas only small amounts of long-chain acylcarnitines were present. This may imply the presence of a mitochondria l carnitine octanoyl transferase or may reflect channelling of long-chain C oA eaters so that they are not available for carnitine palmitoyl transferas e II activity. (C) 1999 Elsevier Science B.V. AU rights reserved.